Frequency is a number of time which a number or a group of numbers appears in a series.
A cumulative frequency is obtained by adding each frequency to the sum of the previous one. When the number in the series are too many, it can be summarized introducing a “class” or “class interval”.
Example: Consider the series: 6, 5, 9, 5, 7, 5, 7, 5, 12, 5, 5, 9, 6 and 6. Draw a frequency table for this series.
Solution
|
Scores
|
Tally
|
Frequency
|
|
5
|
IIII
|
5
|
|
6
|
II
|
3
|
|
7
|
I
|
1
|
|
9
|
II
|
2
|
|
12
|
I
|
1
|
|
Total
|
|
12
|
HISTOGRAM
The word Histogram is derived from a Greek word “histos” meaning a “roast”. It is a bar diagram whose area of a given rectangle is proportional to the frequency of the corresponding class.
The bars are joined together, they can only be drawn vertically and they have no gaps between them.
